1. Field of the Invention
The present invention relates to heat exchangers and more particularly to heat exchangers design to control the temperature of food and medicine transported in personal vehicles.
2. Description of the Prior Art
During long trips in personal vehicles, the most common method currently used for transporting food or medical items that require refrigeration, such as cold drinks or insulin, is to place such items in an insulated box with ice. Most thermally insulated boxes are intended for use at outdoor meals where several people are expected to be present. Since these boxes are designed to hold the food requirements of several people along with sufficient ice for long trips to keep the contents cool for the duration of the trip, they are generally relatively large and occupy considerable space in the vehicle. These boxes are usually kept in the cab of the vehicle where they occupy seat or floor space, often resulting in the discomfort of the passengers. As a trip progresses, the ice melts flooding the bottom portion of the insulated box which requires the food to be packaged such that it cannot be affected by the water, or the water has to be disposed of as the trip progresses. Although dry ice can be substituted for ice produced from water to avoid this problem, it is not readily available.
A less common alternative system for providing refrigeration in personal vehicles uses a similar sized insulated box with a battery operated electrical refrigeration unit. These electrically powered refrigeration units typically plug into the cigarette lighter socket in vehicles to obtain power. Unfortunately, the refrigeration capability is often poor and provides disappointing results, especially during hot weather and on long trips. Added to the problems produced by the bulk of the insulated box is the complication and confining effects of a power cord which often is draped over the front seats to reach an insulated box located on a back seat of the vehicle.
Other than the thermos bottle, there is little that is generally available to keep items such as hot drinks hot for long periods. With thermos bottles, the temperature slowly drops over a period of time until the drink becomes unpalatable. There is no source of heat to make up for the constant loss of heat through the thermos bottle wall and eventually on a long trip the contents can no longer be used.
As presently configured, the heating and air conditioning systems generally found in most vehicles provide little aid in serving as a source of heating or cooling for food or medicine. Such systems are designed to maintain the ambient of the cab of a vehicle within a temperature range of 65 to 80 degrees F. Typically desired temperatures for food are 45 degrees F. for cold food and 140 degrees F. for hot food. The cab temperatures achieved with standard heating and air conditioning systems for vehicles ranges from 20 to 60 degrees away from these desired hot and cold food temperatures.
There is a need to provide a system to accomplish both the heating and refrigeration of food or medicine to desired temperatures while avoiding the bulk, confinement, complication and cost of currently available systems.